Fiber optic connector types

An optical connector is usually male. Two connectors are connected together via an adapter and characterized by two optical parameters, insertion loss and reflected power. Additionally, the connectors must meet geometrical requirements for the ferrule (radius of curvature, apex offset, and protrusion/retraction).

Among the connectors mentioned, SC and LC are the most widely used today. LC takes up half the space of SC, which provides twice the capacity in, for example, a fiber panel. LC is also the standard connector for optical transceivers (SFP).

E2000

Colors:

Jacket on the Cable	Connector and Adapter	Description
Yellow	Blue (PC), Green (APC)	SM, OS2
Gray	Beige	MM, OM1
Orange	Beige	MM, OM2
Turquoise	Turquoise	MM, OM3
Violet	Violet	MM, OM4
Lime Green	Lime Green	MM, OM5

Download cable color codes here.

Connectors - Ferrule Geometry

Most connectors used today have a zirconia ferrule. The diameter of this ferrule is 2.5 mm or 1.25 mm. The ferrule is pre-shaped by the manufacturer, but the person assembling the connector to a fiber performs a final polishing or grinding. This process is critical to achieve the specified optical and geometrical requirements. Similarly, it is crucial that the quality of the ferrule is good enough and that the hole through which the fiber is threaded during assembly is centered. Deviations from this may result in unnecessarily high loss in the connector junction.

PC-polished connector. (PC = Physical Contact)
Such a connector will provide physical contact between the two fibers and a reflected power of <-35 dB (standard requirement) / <-45 dB (typical customer requirement).

APC-polished connector. (APC = Angled Physical Contact)
Such a connector will also provide physical contact between the two fibers. Due to angled end faces, the reflected light will be directed into the cladding mode and lost. APC polishing, therefore, results in very low back-reflected power (<-60 dB).